Inductive Heating Cavity With Class-E Coil for Rapid Aerosol Heating
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Solution Overview
Problem
There is a need for an induction heating device for aerosol-forming substrates, particularly solid substrates used in smoking articles, that can operate without an external power supply, is compact, easy to use, and capable of rapid heat generation to produce aerosol on demand.
Innovation Solution
The device employs a DC power source, a Class-E power amplifier, and an LC load network with a helically wound inductor coil to induce heat in a magnetically permeable and electrically conductive susceptor, which transfers heat to the aerosol-forming substrate, using a cavity for inductive coupling and a microcontroller for temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional combustion process is used to heat the substrate, then high temperatures can be achieved, but the device size becomes large and requires external fuel supply
Solution Approach 1:
The patent replaces the mechanical combustion system with an electromagnetic induction heating system. The induction heating device uses a magnetic field generated by an coil to induce eddy currents in a susceptor, which converts electromagnetic energy directly into heat within the substrate, eliminating the need for combustion chambers, fuel storage, and exhaust systems that would increase device size.
Solution Approach 2:
The patent changes the heating mechanism from thermal combustion to electromagnetic induction, fundamentally altering the energy conversion parameters. Instead of chemical combustion producing heat, the system uses alternating magnetic fields to induce electrical currents that generate heat through resistive heating, achieving comparable temperatures in a more compact form factor.
2Productivity
If an external power supply is used for induction heating, then rapid heat generation is achieved, but the device complexity and portability are reduced
Solution Approach 1:
The patent integrates multiple functions into the handheld device, including the coil assembly that serves both as the induction heating element and as part of the power conversion system. The device incorporates a rechargeable battery, rectifier, and oscillator circuit that work together to generate the high-frequency alternating current needed for induction heating, making the entire power supply system portable and self-contained.
Solution Approach 2:
The patent divides the power supply system into modular components: a rechargeable battery for energy storage, a rectifier circuit for converting AC to DC, and an oscillator circuit for generating high-frequency alternating current. This segmentation allows each component to be optimized independently while maintaining overall system portability and rapid heat generation capability.
3Productivity
If the inductor operates at high power to heat the substrate rapidly, then the inductor temperature becomes excessively high
Solution Approach 1:
The patent introduces a susceptor as an intermediary material between the coil and the substrate. The susceptor absorbs the electromagnetic energy from the coil and converts it to heat through eddy currents, then transfers this heat to the substrate. This intermediary approach allows the coil to operate at lower temperatures while still achieving rapid substrate heating through the susceptor's efficient energy conversion.
Solution Approach 2:
The patent concentrates the heating action locally within the susceptor and substrate interface, rather than heating the entire coil assembly. The electromagnetic energy is focused in the region where the susceptor contacts the substrate, generating heat precisely where needed for aerosol formation while minimizing thermal load on the coil and other device components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for efficient, contactless heating of the substrate, achieving temperatures of 350-400°C in under five seconds, with a compact design and low inductor temperature, enabling on-demand aerosol production.
Implementation Method 1
an alternating magnetic field is induced in the susceptor. This induced alternating magnetic field generates heat in the susceptor
Implementation Method 2
This induced alternating magnetic field generates heat in the susceptor
Implementation Method 3
at least some of this heat generated in the susceptor is transferred from the susceptor to the aerosol-forming substrate arranged in thermal proximity to the susceptor
Data Source
Figure 1
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AI summary
An inductive heating device (1) comprises - a device housing (10) - a DC power source (11), - a power supply electronics (13) comprising a DC/AC inverter including a Class-E power amplifier with a transistor switch, a transistor switch driver circuit, and an LC load network configured to operate at low ohmic load, the LC load network comprising a shunt capacitor and a series connection of a capacitor and an inductor (L2), and - a cavity (14) arranged in the device housing (10), the cavity (14) having an internal surface shaped to accommodate at least a portion of the aerosol-forming substrate (20), wherein the cavity (14) is arranged at the proximal end of the device housing (10) and wherein the inductor (L2) is embedded in the device housing (10) at the proximal end of the device housing (10) to surround the cavity (14) such that the inductor (L2) is inductively coupled to the susceptor (21) of the aerosol-forming substrate (20) during operation.